Software Engineering Quiz 2

Signiture of methods

public static void main(String[] args)

Printing in Java

System.out.println

println gives \n

System.out.println("Answer = " + 3 + 5);

Answer = 35 since 3 will be treated as a string

Ways to define a string (2)

String str1 = new String("Java");
String str2 = "Java"

Pointer:

• Pointer to memory for the class

• No need to delete since Java has garbage collector

Shortcut:

• Special shortcut for strings

• Adds Java to string pool

int x = 3;
int y = 3;
if (x == y) {
	System.out.println("x and y are equal!");
}

Prints fine since comparing values

if (str1 == str2) {
	System.out.println("Equal")
}

if (str1.equals(str2)) {
	System.out.println("Equal")
}

First one won’t print since str1 and str2 initialized differently

Second one is intended method

str1 and str2 both initialized by shortcut method (String str = “Java”)

if (str1 == str2) {
	System.out.println("Equal")
}

Prints fine since both are memory addresses pointing to the same string pool

str3.replace("+", "-")

What does this do?

Nothing! Since strings are immutable, replace returns pointer to newly created string in string pool

Java returns a __ to the _ of the array

pointer, first element

Code to create an array of 10 unknown doubles

double[] data = new double(10);

Code to create an array of ints containing 1,2,3

int[] nums = {1,2,3};

how to call length of an array called nums

nums.length

Contants use the __ keyword

final

Meaning of static keyword

Thing belongs to class itself, not an instance

Thing about accessing null in Java

Can print null, but can’t access null using . notation